1. A change in the electrical charge between the inside and the outside of a membrane. For example, neurons which are receiving signals become momentarily more positively charged than the outside of their membranes.
   
   
2. The turning of polarized light into random light by reflecting it in all directions, so that it no longer vibrates in a single plane.

From the BioTech Dictionary at http://biotech.icmb.utexas.edu/. For further information see the BioTech homenode.

De*po`lar*i*za"tion (?), n. [Cf. F. d'epolarisation.]

The act of depriving of polarity, or the result of such action; reduction to an unpolarized condition.

Depolarization of light Opt., a change in the plane of polarization of rays, especially by a crystalline medium, such that the light which had been extinguished by the analyzer reappears as if the polarization had been anulled. The word is inappropriate, as the ray does not return to the unpolarized condition.

© Webster 1913.